1. Field of the Invention
The present invention relates to a vacuum system for manufacturing semiconductor devices, and more particularly, to a vacuum system which prevents the generation of mist inside a chamber in which a vacuum is being formed, and a method for using the same.
2. Background of the Related Art
Semiconductor device fabrication involves various highly-precise process steps, and the fabrication facility must be equipped to provide a high vacuum state. In order to create and maintain an appropriate degree of vacuum state, vacuum systems are provided for each process according to its process characteristics, for example, an etching process using plasma, a diffusion process to diffuse impurities into a wafer, an ion implantation process to implant impurities into the wafer, and the like.
The vacuum systems for the above mentioned semiconductor device fabrication processes employ various types of vacuum pumps for providing a low vacuum state, a high vacuum state, an ultra high vacuum state, etc., according to the process conditions and the required degree of vacuum.
The vacuum pump functions to absorb the air inside a chamber and to forcibly discharge it outside of the chamber. Typically, a low vacuum pump and a high vacuum pump are installed inside a single chamber, in order to provide gradual formation of a vacuum state.
A conventional vacuum system is constructed such that a connection line is connected to a vacuum pump inside the sealed chamber; and a valve is installed on the connection line and is controlled by a controlling part. The vacuum system is operated in such a manner that the connection line is opened after the chamber is sealed, and the vacuum pump absorbs the air inside the chamber so as to form a vacuum state inside the chamber.
In other words, a low vacuum pump (for example, a dry pump) and a high vacuum pump (for example, a cryo pump) are connected to the chamber via connection lines, and tile valves provided on each of the connection lines are gradually opened. On the other hand, the chamber is prepared for opening to the outside by converting the vacuum state into an atmospheric state, by supplying a vent gas into the chamber in the vacuum state and forming an atmospheric state inside the chamber. Supplying the vent gas prepares the chamber for opening to the outside by increasing the pressure therein to the atmospheric state.
However, at the moment that the valve on the connection line connecting the chamber to the low vacuum pump is opened, the inside of the chamber is abruptly converted into a vacuum state, and mist forms inside the chamber in the form of fine liquid drops, thereby contaminating the inside of the chamber, and damaging the wafers mounted therein.
The mist is formed when vapors in the air in the form of gases condense into drops at a saturation point occurring when the pressure inside the chamber decreases abruptly and the temperature abruptly falls. The drops attach to the surface of the wafer, seriously damaging the wafer.
The present invention is directed to a vacuum system for manufacturing semiconductor devices and a method of using the same, which substantially overcome one or more of the problems of the related arts, and increase the production yield of the wafers by preventing contamination inside chambers due to mist formation, and minimizing the production of the inferior wafers.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the vacuum system for manufacturing semiconductor devices has a vent gas supply apparatus for supplying a vent gas into a chamber in the vacuum state so as to form an atmospheric state required for the opening of the chamber to the outside. The apparatus comprises a heater for preheating the vent gas; a vent gas source for storing the vent gas; a vent gas supply line for transferring the vent gas stored in the vent gas source to the chamber; a valve for opening the vent gas supply line; and a controlling part for controlling the valve by applying an on/off signal to the valve.
In addition, the heater comprises a heating coil for supplying heat to the vent gas with an applied power; and a controlling part for controlling the temperature of the heating coil to be maintained constant. The apparatus may also include a heater installed on the inner wall of the chamber for preventing the generation of liquid drops inside the chamber when the inside of the chamber is converted into the vacuum state.
A method of using a vacuum system of the present invention comprises the steps of preheating the vent gas; supplying the vent gas into the chamber which is sealed with a vacuum state; shutting off the supply of the vent gas; opening the chamber to the outside; unloading processed wafers from the chamber; loading wafers to be processed into the chamber; and forming a vacuum inside the chamber after sealing the chamber. In addition, the vent gas can be continuously supplied while the chamber is opened to the outside, and while the chamber is unloaded and reloaded with wafers.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.